Heretofore fluid sampling in producing and injection wells has been conducted using tools or instruments containing valve controlled sample receiving chambers which remain open while being lowered in the well to become closed after the sampling depth is reached. As a consequence, the samples ultimately received in the chambers may not have accurate correspondence with either the well fluid composition or pressure at the sampling depth in the well, and consequently laboratory analyses may be inaccurate or incomplete in significant respects.
Because of the frequent remoteness of adequate testing facilities for thorough and minute examination of samples taken at the well site, such examination if to be made would require transporting virtually the entire conventional sampling tool over long distances to well equipped laboratories, an often costly and impractical necessity because of equipment bulk and its removal from service.